It is often useful to control an electronic switching circuit in response to different illumination sources; for example, a circuit operative only at night or under reduced ambient light conditions to turn on utilization apparatus in response to an incident light beam. Such circuits are generally known and include a plurality of photosensors each responsive to a respective source of illumination and which are selectively energized in an intended manner to actuate a switching device. Such known circuits are shown, for example, in U.S. Pat. Nos. 1,721,216; 3,083,300; 3,601,614; 3,089,065 and 3,160,757.
In circuits of known construction, the plural photosensors are coupled by analog circuitry to a switching device such as a transistor or other solid state switch, and these photosensors are interdependent such that a variation in the response of one sensor can affect the response of the other ones. As a result, it is often difficult to provide the desired degree of sensitivity or control.